The present invention relates to a process for improving the adhesive properties of surfaces of objects or articles made from copolymers and terpolymers of ethylene and propylene, and in particular to a means for improving the adhesion of paint layers to surfaces of this kind.
As is well known to those skilled in the art objects made from copolymers or terpolymers of ethylene and propylene cannot be easily painted or provided with a lacquer coating because of the insufficient adhesion of the cured layer of paint to the waxy or paraffin-like surface of the materials. It has been found in U.S. Pat. No. 3,607,536 that by first subjecting the surface of such materials to treatment with a sensitizer, such as benzophenone and an organic isocyanate, followed by irradiation with ultraviolet light, the radiation causes an interaction between the isocyanate and the surface substrate thereby providing a surface stratum capable of undergoing strong adhesive bonding. Although the adhesive characteristics of such materials towards lacquer coatings is improved by this technique, the method is objectionable since the need for ultraviolet light requires expensive, special, high-power lamps and radiation chambers.
It has now been surprisingly discovered that it is possible to improve the adhesive properties of a polyolefin surface, in particular towards paint and lacquer without the need for irradiation with light or high-energetic radiation.